Field of the Invention
The present invention relates to a vehicle mounted antenna device and, particularly, to a vehicle mounted antenna device adaptive to a plurality of frequency bands and having such a flatness that it can be incorporated in a hollow body such as a spoiler or a backdoor.
Description of the Related Art
As antenna devices that are mounted on a vehicle and adaptive to a plurality of frequency bands (e.g., AM and FM frequency bands), there are various types of antenna devices, such as a pillar antenna, a roof mount antenna, and a glass antenna. However, the pillar antenna large in protrusion amount is highly likely to be bent due to contact or the like. Further, as for the roof mount antenna, attachment thereof to the roof of a vehicle increases a ground height of the vehicle, so that it is necessary to lay down or remove the roof mount antenna when the vehicle enters a multistory parking space or an automatic car washer. Further, the glass antenna needs to be developed uniquely for each vehicle type, resulting in high development cost. Further, importance is attached to design of the vehicle today and, accordingly, there is required a vehicle mounted antenna device that does not impair appearance of the vehicle as much as possible. Under such circumstances, there are developed various types of antennas that are incorporated in the spoiler so as not to impair the appearance of the vehicle.
For example, there exists an antenna device in which a monopole antenna element is disposed in a space inside the spoiler so as to extend both ends in a left-right direction of the vehicle. Further, Patent Document 1 discloses an antenna device in which an antenna adaptive to AM and FM frequency bands is incorporated in the spoiler. Further, Patent Document 2 also discloses an antenna device in which a radio antenna or a digital TV antenna is disposed in the spoiler.